Tilt Table

A tilt table test is used to verify if a patient has low pressure drops associated with syncope. The heart, of a horizontal patient, pumps blood at a mean arterial pressure of 90 mmHg (12 kPa). The patient faints as soon as the tilt table goes vertical, this means the blood acceleration equal the gravitational acceleration. If the heart rate does not increase to compensate for the change in angle, at what angle would the blood be pumping one half its horizontal pressure.

A. 0

B. 30o

C. 45o

D. 60o

Loading ...

Correct Answer: B.30o.

Pressure is force over area. The cross-sectional area of the of the circulatory system is not changing. The direction of the force appears to be changing. But the blood is still flowing orthogonal to the area, creating the same pressure due to the heart. The only additional element is that gravitational force is being applied.

This additional gravitation force opposes the heart force by a factor of sin(theta) times its weight. We are told that the blood acceleration is equal to g. All we need to find now is when the sin is equal to one half. This will yield a pressure of one half of the horizontal value. This occurs at 30o.

What is the MCAT?

The Medical College Admissions Test (MCAT) is a test administered by the Association of American Medical Colleges (AAMC). The test is designed to test your knowledge in three specific sections; physical sciences such as physics and general chemistry, biological sciences and organic chemistry, and verbal reasoning.

How Should I Study?

The MCAT is a rigorous exam that requires months of planning in order to achieve a great score. It is recommended that you begin your study schedule 3 months prior to your exam date. In addition to answering our practice MCAT questions each day, read this article regarding studying for the MCAT from home.

Register for the MCAT.

The first question many people ask is, “when should I take the MCAT?” The general guideline is to take the MCAT the year before you plan to enter medical school. For example, the class of 2018 should take the MCAT sometime before or during the spring/summer of 2013. Your basic science coursework should be complete by this point.